1. Field of the Invention
The present invention relates to a wind turbine blade and a wind turbine generator having the blade and in particular to a wind turbine blade which is protected from lightning strikes and a wind turbine generator having the blade.
2. Description of the Related Art
In general, a lightening protection system of a wind turbine blade is configured such that lightning strike is captured in a plurality of receptors (metallic lightening receiving section) mounted on a blade surface, and lightening current is conducted to the ground through the inside of the blade, a rotor hub, a nacelle and a tower by means of a downconductor connected to the receptors. There are many types of receptors such as a circular receptor, a rod receptor, and a blade-type receptor. Further, conductive tapes, conductive meshes and conductive diverter strips (metal pieces mounted discontinuously on the blade surface) can be used as the receptors.
FIG. 1A is a schematic view showing an exemplary structure of a wind turbine blade having a common lightening protection system. The wind turbine blade 101 has a rod receptor 112 embedded in a tip of the blade body 111, disk receptors 113 embedded in the blade, downconductors 121 (a leading edge receptor and a trailing edge receptor) which are connected to the rod receptor 112 and the disk receptors 113 and installed across the inner space of the blade body 111. As shown in FIG. 1B, the disk receptors 113 includes, for instance, a conductive circular disk 131 and a wire 133 for connecting the disk 131 and the downconductors 121. When lightning strikes the receptors (112, 113), the lightning is conducted to the ground from the receptors through the downconductors, the inner space of the blade, the rotor hub, the nacelle and the tower.
A method of registering lightning strike in the blade of a wind turbine is disclosed in U.S. Pat. No. 7,508,186. A wind turbine generator as described in U.S. Pat. No. 7,508,186 includes receptors mounted in several places on the blade surface. The receptors are earthed to the ground via a conductive wire in the blade.
A lightning protection device of a wind turbine blade and a method of assembling the lightning protection device are disclosed in US2009/0053062. The lightning protection device has a tip receptor assembly and an intermediate receptor assembly. The tip receptor assembly has receptors which are mounted, in particular to, the tip end part of the blade where the blade profile becomes smaller, and has a simple structure so as to be readily assembled. The intermediate receptor assembly has a receptor which is set at the outer surface of the blade so as to exhibit an effective countermeasure against increasing of the air pressure in the blade upon a lightning striking the blade. The lightning current is discharged to the ground from the receptors through connection equipment such as lead wires laid through the inside of the blade, the windmill body and bypass brushes. A base plate made of an electrically conductive material and connected to the wires is embedded in the blade, and receptors are secured and supported to the base plate.